Referrals as a possible way to fund free software work

I've been thinking about ways to solve a particular dilemma. It
involves free software / open source software. Here's a typical
problem: I've written something which does some pretty neat stuff with
software defined radio techniques. The main system specifically decodes
Motorola SmartNet and is based off GNU Radio and gr-smartnet plus a
bunch of my own work.

It took a non-trivial amount of time to get this stuff working. None of
it came anywhere close to being usable when I originally got my hands on
it. I ran into all sorts of crazy problems with this system which I had
never touched before, and had to plow all kinds of time, energy and
money into making the system which exists today. It was hellish.

Two weeks disappeared into trying to make this thing log audio: it
arrived around 11 AM on July 15th and I didn't have a viable demo web
page with real recordings until July 29th. It took even more work to
make it into the
web application
it is today.

Given all of this, how should I react when people show up at my web site
and then get annoyed because there's no source code to download?

There are folks who get in touch with me because they want some custom
radio work. We talk about what needs to be done, come to an agreement,
and then I build something. I receive compensation for my work and
everyone is happy.

Maybe there's a solution just waiting to be found here. I suspect the
people who just want to download something are not likely to engage my
services for systems programming. However, I bet they know people who
need that sort of work done, and could help with some introductions. If
those introductions turned into some gigs, it might be enough to fund
the release of some of these projects.